T II E 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 

 NOVEMBER 1855. 



XL. On the Passage of Electric Currents through Rarefied Air. 

 By P. RiEss*. 



AN interesting observation has lately been made by M. Gau- 

 gain iu Paris. He allowed a magneto-induction current 

 to pass between metallic knobs enclosed in a glass receiver con- 

 taining rarefied air, one of which knobs, with the exception of a 

 very small portion, was coated with an insulating substance f. 

 Besides the glass receiver, or electric egg, a galvanometer was 

 introduced into the circuit, the needle of which was strongly 

 deflected when the naked knob was negative, i. e. when the 

 current passed from the covered to the naked knob, but suffered 

 no deflection when the current was reversed. Thus to the inter- 

 ruption current J of the induction apparatus was ascribed the 

 property of passing through the electric egg in one direction 

 only, that is, from the coated to the naked knob, and on this 

 account the egg was called an electric valve. The following in- 

 vestigation will show that this conclusion is unfounded, and that 

 the name, at least in the above sense, is inappropriate. 



In order to repeat Gaugaiu's experiment, I provided myself 

 with a short glass cylinder closed at each end with metallic 

 jilatesj the lower plate, as well as its attached rod and knob, 

 with the exception of a small portion of the latter about the size 

 of a pin's head, were coated with melted sealing-wax : about 

 three-quarters of an inch above the coated knob was a similar 



* From the Report of the Academy of Science at Berlin, June 18, 1855. 



t Comptes Rendus, vol. xl. p. 640. Phil. Mag. vol. x. p. 207. 



X The induced currents caused by interrupting and closing the circuit of 

 the primary or inducing current, are for the sake of brevity called inter- 

 ruption current and contact current, respectively. 



Phil. May. S. 4. Vol. 10. No. Q7, Nov. 1855. Y 



